Communication devices such as mobile phones have extended their capabilities to offer the connection to the Internet. To handle increasing communication data, technologies such as Long Term Evolution (LTE)-Advanced have been developed. LTE-Advanced employs Carrier Aggregation (CA) technology to enhance throughput. For example, Inter Band Non Contiguous CA simultaneously uses LTE bands of, for example, 800 MHz and 2 GHz to achieve a wider band, higher speed, and a greater amount of data in communications. Simultaneous transmission or simultaneous reception of two signals may be performed alone.
For smaller mobile phones, a common antenna transmits and/or receives signals in frequency bands of multiple communication systems. Japanese Patent Application Publication No. 2004-40322 discloses a technique that uses a diplexer coupled to an antenna to transmit and/or receive signals in different frequency bands via a single antenna.
When a diplexer is used to simultaneously transmit and/or receive signals in different frequency bands via a single antenna, multiple transmit/receive systems are simultaneously coupled to the diplexer. At this time, a notch is formed in a diplexer in the frequency band of a communication system.